OpenSAT

Draw a radius from the center of the circle to one endpoint of the chord, and draw another radius to the other endpoint of the chord. This forms an isosceles triangle with the chord as the base. The altitude of this triangle from the center of the circle bisects the chord. This altitude forms a right triangle with one leg being 4 centimeters (half of the chord) and the hypotenuse being 5 centimeters (the radius). Using the Pythagorean theorem, the other leg of the right triangle (which is the distance between the center of the circle and the chord) has length $\sqrt{5^2-4^2} = \sqrt{9} = 3$ centimeters.